Synthesis for the Mesomer and Racemate of Thiophene-Based Double Helicene under Irradiation

In this work, the racemate and mesomer of the thiophene-based naphthalene-cored double helicenes (1) were obtained efficiently by one-pot photocyclization of 1,1,2,2-tetrakis­(dithieno­[2,3-b:3′,2′-d]­thiophen-2-yl)­ethene in the presence of iodine in dry benzene. The structure of meso-1a was confirmed by single crystal X-ray analysis. The chiral resolution of the racemate was carried out by chiral HPLC, and the chiral properties, such as CD spectra, optical rotations, and half-life of enantiomers were characterized.